It is known that current limiting elements or ballasts necessary for lighting a discharge lamp include induction elements such as a magnetic core, such as silicon steel sheet, on which a copper wire is wound, capacitive elements using a dielectric such as plastic film and paper and resistance elements using a nichrome wire. All these elements have enough current capacity necessary for operating a discharge lamp. However, they have the disadvantage that their weights and sizes are large. Moreover, the resistance elements exhibit a high power loss.
Accordingly, an object of the present invention is to improve the above-mentioned disadvantages of the conventional arts and to provide a lighting apparatus for a discharge lamp which is small-sized and exhibits a low power loss.
The lighting apparatus for a discharge lamp according to the present invention is characterized in that there is used a current limiting device utilizing the dependency of an impedance of a ferroelectric polycrystalline ceramic comprising mainly barium titanate on a voltage.